Commentary: Physical activity and obesity; scientific uncertainty and the art of public health messaging

The article by Luke and Cooper published in this edition of the International Journal of Epidemiology proposes that physical activity energy expenditure plays no role in either causing or moderating the obesity epidemic and that current guidelines for physical activity should be reformulated. We would take issue with these conclusions, arguing that the relationship between physical activity and the development of weight gain at the individual level and the link between secular trends in activity and the prevalence of obesity at the population level are complex and uncertain. Given this scientific uncertainty, we would argue for caution when considering altering public health messages as the risks for confusion of the public are considerable.